This invention relates generally to shell and tube heat exchangers, and, more specifically to mini-vortex generators and sinuous baffles used in shell and tube-type heat exchangers.
Heat transfer is an important engineering concern for many process. Heat exchangers are a well known apparatus for transferring heat from one medium to another. There are many types of heat exchangers, including for example shell and tube designs, double pipe type shell and tube designs, plate and frame designs, plate-fin designs, and others. These heat exchangers are used in many industries, including those engaged in generating energy, producing chemicals, refining petroleum products, and air conditioning. All of these industries would stand to benefit from a more efficient heat exchanger design.
A common goal in the design of shell and tube-type heat exchangers is to enhance heat transfer while trying to keep the associated pressure drop low, or in other words to maximize the ratio of the heat transfer coefficient to the pressure drop. The higher the pressure drop, the more energy must be expended to pump the fluids through heat exchanger.
A problem with existing shell and tube type heat exchanger designs is a failure to maximize the heat transfer coefficient while keeping the pressure drop to a minimum. This is evidenced in shell and tube exchangers utilizing segment type baffles, which generate flow perpendicular to the tube bundle, which is otherwise known as crossflow. These baffles have a high heat transfer coefficient but also have a high pressure drop resulting from the crossflow. Alternatively, current commercial designs utilizing grid baffles with flow parallel to the tube bundle, have a low pressure drop but have a less favorable heat transfer coefficient. Consequently the overall efficiency, as measure by the ratio of the heat transfer coefficient to pressure drop, is not maximized in current shell and tube type heat exchangers.
What is needed is a shell and tube type heat exchanger that improves upon the heat transfer coefficient to pressure drop ratio of current shell and tube heat exchangers utilizing grid type baffles.
The invention satisfies this need. The invention is a shell and tube type heat exchanger that provides a greater heat transfer coefficient to pressure drop ratio and is thus more efficient.
The heat exchanger has a shell and a tube bundle inside the shell. The tube bundle includes a plurality of substantially parallel tubes for passage of a first fluid. At least a portion of the tubes have a mini-vortex generator on their exterior surface. The heat exchanger further includes a grid baffle between the tubes, a tube inlet for passage of the first fluid into the tubes, and a tube outlet for passage of the first fluid out of the tube. The shell has a shell outlet for passage of a second fluid into the shell and exterior to the tubes and a shell outlet for withdrawing a second fluid from the shell.
In another embodiment, the heat exchanger has a shell and a tube bundle inside the shell. The tube bundle includes a plurality of substantially parallel tubes for passage of a first fluid. In this embodiment, the heat exchanger has sinuous baffles for supporting the tubes. Each sinuous baffle includes a plurality of wiggle bar tube support members disposed between the tubes. The heat exchanger further includes a tube inlet for passage of the first fluid into the tubes and a tube outlet for passage of the first fluid out of the tube. The shell has a shell outlet for passage of a second fluid into the shell and exterior to the tubes and a shell outlet for withdrawing the second fluid from the shell.
In another embodiment, the heat exchanger has sinuous baffles and at least a portion of the tubes of the heat exchanger have a mini-vortex generator on their exterior surface.
In operation, when the first and second fluid are passed countercurrent, cocurrent, or in multi-pass substantially parallel flow, and when the fluids are at different temperatures, a transfer of heat occurs between the fluids.